The present invention relates to a method for heating one or more streams from a refinery process. More in detail, the present invention relates to the heat integration between petroleum refinery processes and petro-chemistry processes.
US patent application No 20120/24749 relates to method for cracking a hydrocarbon feed, the method comprising: providing a hydrocarbon feed to a hydrocarbon pyrolysis unit to create cracked effluent; passing at least a portion of the cracked effluent from the hydrocarbon pyrolysis unit through a first heat exchanger; separating the at least a portion of the cracked effluent from the first heat exchanger into a gaseous effluent and a liquid effluent; passing at least a portion of the gaseous effluent through a second heat exchanger; passing at least a portion of the effluent from the second heat exchanger to a fractionator; recovering heat from the at least a portion of the effluent in the second heat exchanger by passing a utility fluid through the second heat exchanger; and recovering heat from the at least a portion of the cracked effluent in the first heat exchanger by passing the utility fluid from the second heat exchanger through the first heat exchanger. This document teaches to use the heat from a stream from a petro-chemistry process for heating another stream, i.e. the utility fluid.
EP 0 205 205 relates to a transfer-line exchanger and a method for cooling of a fluid such as a cracked reaction product, the transfer-line exchanger of is a shell and tube type heat exchanger having two or more separate heat exchanging sections but only one inlet and one collection header, the separate sections being joined by intermediate tubes. in the cooling of a cracked hydrocarbon product having a temperature from 750° to 900° C., in the first heat exchanging zone, high pressure steam can be produced using water at its boiling temperature and pressure as the cooling fluid in that zone. Alternatively, in the second heat exchanging zone, the partially cooled, cracked reaction product, having a temperature from 450° to 650° C. can be further cooled to produce lower pressure steam. This document teaches to cool a cracked reaction product by using a transfer-line exchanger of the shell and tube type.
U.S. Pat. No. 2,294,126 relates to process for distilling and fractionating crude petroleum oil in heat exchange with heat treated hydrocarbon products undergoing fractionation, which comprises contacting the hot products produced by cracking a hydrocarbon distillate to lower boiling hydrocarbons with a catalytic adsorbent to complete the cracking reaction and to precipitate tars and fuel oil higher boiling than gas oil, passing the remaining hot products in the vapor phase without substantial condensation into contact with the hot products obtained by a non-carbonizing splitting treatment of a reduced crude to strip volatiles therefrom. This document teaches the unification of the heated product separation with the preparation of charging stocks in order to eliminate heat dissipating vessels, such as partly detached towers, and the multiple connections, found in the usual vast array of apparatus used in cracking systems.
Petroleum refining processes are the chemical engineering processes and other facilities used in petroleum refineries (also referred to as oil refineries) to transform crude oil into useful products such as liquefied petroleum gas (LPG), gasoline or petrol, kerosene, jet fuel, diesel oil and fuel oils. Petrochemicals are chemical products derived from petroleum and examples thereof are olefins (including ethylene, propylene, and butadiene) and aromatics (including benzene, toluene and xylene isomers). Oil refineries produce olefins and aromatics by fluid catalytic cracking of petroleum fractions. Chemical plants produce olefins for example by steam cracking of natural gas liquids like ethane and propane. Aromatics are for example produced by catalytic reforming of naphtha.
Nowadays, industrial plants where petroleum refinery processes, e.g. a steam cracker unit, are carried out are separated from industrial plants where petrochemical processes, e.g. a crude distillation unit (CDU), are carried out. Such a separation means in fact that no heat integration takes place between these processes, i.e. petroleum refinery processes and petrochemical processes.
The crude furnace of a crude distillation unit heats up oil to temperatures of approximately 350° C. Heat is normally provided by the combustion of gas or oil. A crude-oil atmospheric-distillation (or topping) plant makes it possible to obtain distillates (made up of the overhead product and the side fractions) and the residue, by the physical separation of a mixture of homologous components. This separation, which makes use of the differing distributions of the components between the vapor and the liquid phases, takes place in stages operating in conditions close to equilibrium. The separation of the various fractions of the distillate is achieved by fractional condensation of the vapors of the distillate, which is an operation requiring heat removal. In the case of a distillation column (or still) this heat removal is carried out by means of a series of refluxes: external reflux, consisting of part of the condensed overhead product, and intermediate refluxes, consisting of liquid withdrawn from the column and, after cooling, returned to it at a point above that from which it was withdrawn. Intermediate refluxes are commonly called circulating refluxes or pump around. The feed, coming from the storage tanks, is pumped to the heater, having been preheated with heat recovered, by means of a heat exchanger, from the overhead vapors, side fractions, intermediate refluxes and the atmospheric residue. After having been heated in the heater to the temperature required for the operating conditions, the feed is transferred to the flash zone of the atmospheric column by means of a transfer line, where the separation takes place into the vaporized fractions (equivalent to the total of the distillates) and the liquid residue.
In a steam cracker furnace a hydrocarbon feed is heated to temperatures above 800° C. and then rapidly cooled (quenched indirectly) to at least below 600° C., generating very high pressure steam. The gas is further cooled by high pressure steam generation and other forms of heat recovery and eventually by water quench, air coolers, and water coolers.
Steam cracking is an energy intensive process. Very high temperature heat is required for the steam cracking process. Lower temperature heat is or can be recovered from the process. However, the separation process requires mainly cold and little need for (low exergy) heat in the temperature range of 200-400° C., this applies especially for steam crackers with light feed stocks.
In addition, refining of crude oil requires heat in the temperature range of 200-400° C.: crude oil is heated to approximately 350° C. in the crude furnace before entering the atmospheric tower. In the crude furnace oil or gas (high exergy) is fired to provide heating at relatively (low exergy) mild temperatures (compared to steam cracking). Such a crude furnace may have good energy efficiency but is rather poor on the exergy efficiency.